The present application claims priority to Italian Patent Application Serial No. MI 2000A 000450, filed Mar. 8, 2000.
The present invention relates to a torque wrench with variable-arm clicker mechanism.
As is known, there are various torque wrenches in existence, in particular equipped with a variable-arm clicker mechanism, which are used for applying a pre-established tightening torque on fastening devices such as bolts, nuts and similar.
Torque wrenches generally have a tubular body, equipped with a handgrip, on which is applied a ratchet gear mechanism having, on one face, a suitable protruding part or cavity which allows it to mate with the fastening device that is to be tightened.
This purpose of this ratchet gear is to form a solid connection, only in the tightening direction, with a portion of the mechanism which mates with the fastening device and with the tubular body, thus tightening the fastening device.
Inside the tubular body is a so-called xe2x80x9cclickerxe2x80x9d mechanism which, when the pre-established tightening torque has been applied on the fastening device, allows a further limited rotation of the tubular body in the tightening direction without this additional rotation having any effect on the fastening device.
In this way, when the user feels this clicking rotation in the tightening direction, he understands that the desired torque has been applied on the fastening device.
An example of these torque wrenches is described in the patent for an industrial invention No. IT 1191798.
It presents, among other things a torque wrench clicking and resetting mechanism, operated by a spring, for determining the clicking movement of the above-mentioned clicker mechanism.
The torque wrench reset mechanism comprises a first transmission lever, which is hinged on a pin arranged substantially at the same height as a second pin on which is hinged a second transmission lever.
When the pre-established tightening torque is applied on the nut or bolt to be tightened, one of the above-mentioned levers rotates in the opposite direction to the tightening direction, causing consequent rotation of the second lever and these rotations take place with a clicking movement, thus preventing further tightening of the nut or bolt once the pre-established tightening torque has been applied on them.
Although a torque wrench such as the one described is able to perform the function for which it was designed, some interesting and important improvements may be made.
In this torque wrench there are in fact a high number of components which are used to realise the linkages necessary to make the clicking and reset of the wrench.
Moreover some components are difficult to make and are therefore expensive, and are also subject to premature wear because they have areas with concentrated loads that are too high.
The aim of the present invention is therefore to realise a torque wrench with a variable-arm clicker mechanism, with a distinctly simpler construction than the prior art.
A further aim of the present invention is to realise a torque wrench with a reduced number of components.
Another aim of the present invention is to indicate a torque wrench with high repeatability, reliability and long life.
Not the least aim of the present invention is to indicate a torque wrench that is easy to realise and therefore with low costs.
These and other aims are achieved by a torques wrench with a variable-arm clicker mechanism, comprising a substantially tubular body (41), equipped with a handgrip (18) from which protrudes a ratchet gear element (4) to engage a blocking device (14) which must be tightened, wherein inside said tubular body (41) is said variable-arm clicker mechanism, said variable-arm clicker mechanism comprising a main lever (2) having a first end and a second end and having on said first end said ratchet gear element (4) and on said second end a T shaped element (5), said main lever (2) being mounted on said tubular body (41) by means of a first pin (3), wherein said variable-arm clicker mechanism has a pair of parallel intermediate levers (6), hinged on a fulcrum (10), which is integral with a movable carriage (9), said parallel intermediate levers (6) being extended within said movable carriage (9) through a pair of slots (31, 32) and being connected by means of a second pin (12) to a pair of small levers (22) hinged by a third pin (21) onto a roller (15) which acts on a push rod (20) to operate a resilient means (16).
Further characteristics of the present invention are also defined in the subsequent claims.